Syringe assembly

ABSTRACT

A syringe assembly comprising, a syringe having a chamber for retaining fluid, and a plunger having one end received in the chamber for pumping fluid out of the chamber. The syringe assembly has means for limiting the amount of pressure generated by the syringe during pumping of fluid.

This is a continuation, of application Ser. No. 853,962 filed Nov. 22,1977 abandoned, which is a division of Ser. No. 776,147 filed Mar. 101977, U.S. Pat. No. 4,074,714 which is a division of Ser. No 702,164filed July 2, l976 U.S. Pat. No. 4,030,497, which is a division of Ser.No. 627,982 filed Nov. 3, l975, which is a continuation-in-part of Ser.No. 509,757 filed Sept. 27, 1974 abandoned.

BACKGROUND OF THE INVENTION

The present invention relates to pumping devices, and more particularlyto syringes.

Syringes are in common use today by physicians, nurses, and otherhospital personnel for a variety of purposes. Frequently, syringes havebeen utilized to pump fluid into a body cavity of a patient or a cavityin a therapeutic device under circumstances where the pressure attainedin the cavity should be limited to a predetermined value. For example,during a spinal anesthesia procedure an anesthetic solution is pumpedfrom a syringe through a needle into the sub dural space which isessentially an inelastic pouch, and thus only a specified maximum amountof the solution should be pumped into the space as determined by thepressure in the space. Similarly, various types of cardiovascularcatheters are often threaded into blood vessels, after which a balloonadjacent the distal end of the catheter is inflated through use of asyringe. If the balloon is overinflated, particularly when the catheteris placed in a smaller vessel, the vessel may be ruptured. Numerousother catheters, such as endotracheal tubes and Foley catheters, arefrequently provided with retention balloons which should not beoverinflated, particularly when the balloon is obstructed by a bodypassage.

Few of the hospital personnel realize the considerable pressures whichcan be generated by a hand-operated syringe. For example, a 10 c.c.syringe may readily generate pressures in the range of 50-60 lbs./sq.in., the smaller syringes being capable of developing greater pressuresfor the same amount of force applied to the syringe plunger. It is thusapparent that considerable care must be exercised by the user when asyringe is utilized to pump fluid into a cavity space where only alimited amount of pressure is desired. In the past, tactile sense hasbeen used when forcing the plunger into the syringe to determine whenthe maximum pressure has been attained by resistance to plungermovement. Such a procedure produces speculative results, at best, inpreventing harm to the patient, particularly since the syringe mayreadily generate relatively high pressures.

SUMMARY OF THE INVENTION

A principle feature of the present invention is the provision of asyringe assembly of simplified construction which prevents damage to apatient during use.

The syringe assembly of the present invention comprises, a syringehaving a chamber for retaining fluid, and a plunger having one endreceived in the chamber for pumping fluid out of the chamber. Thesyringe assembly has means for limiting the amount of pressure generatedby the syringe during pumping of fluid.

Thus, a feature of the present invention is that the syringe assemblyprevents generation of an excessive amount of pressure during use toprevent possible damage to the patient.

Another feature of the invention is that the limiting means actuates ata predetermined pressure to relieve pressure in the syringe chamber.

A further feature of the invention is that the syringe assembly mayprovide means for indicating when the predetermined amount of pressurehas been attained.

Still another feature of the invention is that in one embodiment thelimiting means is associated with an extension of a syringe barreldefining the syringe chamber.

A feature of the invention is that in one embodiment the limiting meansis associated with an adapter for the syringe.

Yet another feature of the invention is that in one embodiment thelimiting means prevents movement of the plunger into the syringe chamberwhen the predetermined amount of pressure has been attained.

A further feature of the present invention is the provision of a methodfor performing an epidural and a spinal anesthesia procedure.

Further features will become more fully apparent in the followingdescription of the embodiments of this invention and from the appendedclaims.

DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 is a sectional view of one embodiment of the syringe assembly ofthe present invention as attached to a hollow needle;

FIG. 2 is a fragmentary sectional view of pressure limiting means in thesyringe assembly of FIG. 1 as actuated above a predetermined pressure;

FIG. 3 is a fragmentary elevational view of the syringe assembly of FIG.1;

FIG 4 is a fragmentary sectional view of another embodiment of thesyringe assembly of the present invention as being applied to acatheter;

FIG. 5 is a sectional view of an adapter in another embodiment of thesyringe assembly of the present invention;

FIG. 6 is a sectional view of an adapter in another embodiment of thesyringe assembly of the present invention;

FIG. 7 is a sectional view taken substantially as indicated along theline 7--7 of FIG. 6;

FIG. 8 is a sectional view of the adapter of FIG. 7 illustratingpressure limiting means as actuated above a predetermined pressure;

FIG. 9 is a sectional view of an adapter in another embodiment of thesyringe assembly of the present invention;

FIG. 10 is a sectional view of the adapter of FIG. 9 illustrating valvemeans in the adapter as actuated above a predetermined pressure:

FIG. 11 is a sectional view taken substantially as indicated along theline ll--11 of FIG. 9;

FIG. 12 is a sectional view of another embodiment of a syringe assemblyof the present invention;

FIG. 13 is a sectional view of another embodiment of a syringe assemblyof the present invention;

FIG. 14 is a sectional view of an adapter in another embodiment of thesyringe assembly of the present invention;

FIG. 15 is a fragmentary elevational view of another embodiment of asyringe assembly of the present invention;

FIG. 16 is a fragmentary sectional view of the syringe assembly of FIG.15;

FIG. 17 is a front plan view of another embodiment of a syringe assemblyof the present invention;

FIG. 18 is a fragmentary sectional view taken substantially as indicatedalong the line 18--18 of FIG. 17; and

FIGS. 19 and 20 are fragmentary sectional views of additionalembodiments of a syringe assembly of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to FIGS. 1-3, there is shown a syringe assembly or syringemeans generally designated 20 comprising a syringe 22. The syringe 22has a hollow barrel 24 having a chamber 26 for retaining fluid. Thesyringe also has a plunger 28 having a flexible plug 30 adjacent one end32 of the plunger received in one end of the chamber 26. The plug 30sealingly engages against the inner surface 33 of the syringe barrel 24,with the plunger being pushed into the chamber 26 to pump fluid out ofthe chamber.

The syringe 22 has an extension or extension means 34 projecting from anend of the barrel 24 remote the plunger 28, with the extension 34 havinga tip 36 receivable in the hub H of a hollow needle N. Of course, thetip 36 of the syringe extension 34 may be connected to any othersuitable device, such as a catheter, as described below. The extension34 has a passageway 38 which communicates with the syringe chamber 26and the hollow needle N, when attached, and has a flexible balloon 40which communicates with the passageway 38 through an opening 42 in thewall of the extension 34. The balloon 40 comprises a flexible sleevewhich surrounds the extension 34, and has a pair of edges 44a and 44bsecured to the outer surface of the extension 34 by suitable means 46aand 46b, such as adhesive. Thus, the balloon or sleeve 40 has its edges44a and b sealed peripherally around the extension 34, such that itdefines a cavity 48 intermediate the sleeve and the outer surface of theextension 34 which communicates through the opening 42 with thepassageway 38.

The balloon 40 is constructed to inflate when a predetermined pressurehas been reached in the passageway or chamber of the syringe, theparticular pressure at which the balloon inflates being selected for theparticular use contemplated for the syringe assembly. The pressure atwhich the balloon inflates may be controlled by a number of factorsincluding the particular material used for the balloon, such as latex,and the thickness, durometer, and elasticity of the balloon, as well asthe transverse and longitudinal radii of the balloon, according to thelaw of Laplace which holds that the pressure required to inflate aballoon is directionally proportional to its tangential tension andinversely proportional to its transverse and longitudinal radii.

In use of the syringe for a spinal anesthesia procedure, the chamber isfilled with fluid, such as an anesthetic solution, and the syringe tip36 is attached to the hub H of the needle N, after which the tip T ofthe needle may be advanced through the tissue t, the potential epiduralspace e, and the dura mater d of the patient's body, and inserted intothe sub dural space s adjacent the spinal cord s'. The anestheticsolution is then ejected from the syringe chamber 26 into the sub duralspace s by pushing the plunger 28 into the syringe chamber. Since thesub dural space is essentially an inelastic blind pouch filled withfluid, as shown in FIG. 1, and under a positive pressure, the balloon 40of the syringe is selected to inflate at a predetermined pressuregreater than the pressure in the sub dural space s. Consequently, as thesolution is pumped into the sub dural space, the pressure builds up inthe space until it reaches the predetermined pressure, after which theballoon 40 inflates, as shown in FIG. 2, and relieves pressure build upin the space, thus preventing harm to the patient. Accordingly, theballoon 40 serves to limit the amount of pressure generated by thesyringe, and prevents ejection of further fluid into the needle N andsub dural space after the predetermined pressure has been attained. Theinflated balloon also serves as an indication to the user that thepredetermined amount of pressure in the space or cavity has beenreached, and that the plunger should not be pushed further into thesyringe chamber 26.

Another embodiment of the syringe assembly 20 of the present inventionis illustrated in FIG. 4, in which like reference numerals designatelike parts. In this embodiment, the extension means 34 includes anadapter 50. If desired, a conventional syringe 22 may be used having astandard luer tip 36'. The adapter 50 has a tip 36 adjacent one end forconnection to a catheter C', or other suitable device, such as theneedle N, and a recess 52 adjacent the other end of the adapter forattachment to the tip 36' of the syringe 22. A passageway 38 extendslongitudinally through the adapter 50, and communicates between thesyringe chamber 26 and the catheter C' when the ends of the adapter areconnected to the syringe and catheter. The adapter 50 has a flexiblesleeve or balloon 40 extending around the adapter and having its ends44a and b secured peripherally around the outer surface of the adapterby suitable means 46a and b, such as adhesive. The sleeve 40 defines acavity 48 intermediate the sleeve and the outer surface of the adapter50 which communicates with the passageway 38 through the opening 42.

In use, after the syringe has been filled with fluid, the adapter 50 isattached to the tip 36'of the syringe 22, and the tip 36 of the adapter50 is attached to the catheter C'. The catheter may be of a type havinga lumen L which communicates between a proximal end P of the catheterand a cavity C" underlying a balloon B adjacent a distal end D of thecatheter. For a cardiovascular catheter, as shown, the catheter ispreviously threaded through a vessel, and the balloon B is inflatedthrough the lumen L by pumping fluid from the syringe chamber 26. Whenthe partially inflated balloon B becomes obstructed by the wall of thevessel, and a predetermined amount of pressure is developed in thecavity C" defined by the balloon B, the flexible sleeve 40 inflates tolimit the amount of pressure generated by the syringe and preventoverinflation of the balloon B, which otherwise might rupture thevessel.

It is apparent that the pressure limiting or indicating means associatedwith the syringe assembly of the present invention may be incorporateddirectly onto the syringe itself, as previously described, or may beplaced on the adapter which is connected to the syringe. In either case,the device operates in a similar manner to prevent harm to the patient.Thus, for purposes of previous and future discussion, it is immaterialwhether the limiting or indicating means is associated with the adapteror the syringe itself in the syringe assembly, with the exception of thedevices described in connection with FIGS. 12 and 13.

Another embodiment of the adapter 50 in the syringe assembly 20 isillustrated in FIG. 5, in which like reference numerals designate likeparts. In this embodiment, the adapter 50 includes an outwardlyextending thumb 56 having a channel 58 communicating with the passageway38. The adapter 50 has a flexible sleeve 40 extending peripherallyaround the thumb 56 and having its edges 44a and b secured peripherallyaround the thumb by means 46and b, such as adhesive, thus defining acavity 48 communicating with the channel 58 and passageway 38 throughthe opening 42. The sleeve or balloon 40 inflates, as previouslydescribed in connection with the syringe assembly of FIGS. 1-4, to limitthe amount of pressure generated in the passageway 38 and the syringechamber.

A further embodiment of the adapter 50 in the syringe assembly 20 of thepresent invention is illustrated in FIGS. 6-8, in which like referencenumerals designate like parts. In this embodiment, a balloon 40' has itsperipheral edges 44' sealed by suitable means 46', such as adhesive, toan outer surface 60 of the adapter 50 to define the cavity 48, whichcommunicates with the passageway through the opening 42. As shown inFIG. 8, the balloon 40' inflates at a predetermined pressure, aspreviously described, to limit the amount of pressure generated by thesyringe assembly.

Another embodiment of the adapter 50 in the syringe assembly 20 of thepresent invention is illustrated in FIGS. 9-11, in which like referencenumerals designate like parts. In this embodiment, a valve element 64 issupported in a chamber 66, with a head 67 of the valve element 64 havinga face 68 for sealing against a seat 70 in the chamber 66. The head 67has a stem 72 extending from an end of the head remote the face 68, withthe stem 72 being received in a cavity 74 in the adapter 50. A helicalspring 76 surrounds the stems 72 and extends between a back surface 78of the cavity 74 and a back surface 80 of the head 67. The adapter 50has a channel 82 communicating between the passageway 38 and the chamber66 adjacent the seat 70, and a pair of channels 84a and 84bcommunicating between the chamber 66 and an outer surface 86 of theadater 50. As illustrated in FIG. 9, the spring 76 biases the head 67 ofthe valve element to a first position with the face 68 sealing againstthe seat 70 to prevent passage of fluid from the channel 82 into thechamber 66. However, when a predetermined amount of pressure is reachedin the passageway 38, the spring 74 permits movement of the valveelement to a second position with the face 68 of the head 67 spaced fromthe seat 70, as shown in FIG. 10, and fluid then passes from thepassageway 38 through the channel 82, chamber 66, and the channels 84aand b to the outer surface 86 of the adapter 50, as indicated by thedirection of the arrows in the drawing. Thus, the valve means isactuated at a predetermined pressure to relieve pressure in thepassageway 38, and limit the amount of pressure generated by the syringeassembly. The pressure at which the valve means is actuated may beselected by the particular structure of the valve assembly, such as theparticular helical spring 74 utilized in the adapter 50.

Another embodiment of the syringe assembly 20 of the present inventionis illustrated in FIG. 14, in which like reference numerals designatelike parts. In this embodiment, the adapter 50 has an outer transparentcylindrical shield 51 defining a chamber 53, and a pair of extensions55a and 55b extending into the chamber 53 and partially defining thepassageway 38'. The tubular sleeve 40 has its ends received on theextensions 55a and b and secured in place by suitable means 46a and b,such as adhesive. The sleeve 40 expands to limit the amount of pressuregenerated by the syringe assembly, as previously described, and isvisible to the user through the transparent shield to determine when thesleeve has expanded. The shield serves to protect the sleeve, and air ispermitted to pass from the chamber 53 through a vent 57 in the shield topermit expansion of the sleeve.

Another embodiment of the syringe assembly 20 of the present inventionis illustrated in FIGS. 15 and 16, in which like reference numeralsdesignate like parts. In this embodiment, the flexible balloon or sleeve40 extends around the syringe barrel 24. The sleeve 40 is secured to anouter surface 152 of the syringe 22 by suitable means 46a and b, such asadhesive, adjacent the edges 44a and b of the sleeve 40, in order todefine a cavity 48 intermediate the sleeve 40 and barrel 24 whichcommunicates with the syringe chamber 26 through an opening 42 in thebarrel 24. The sleeve 40 inflates above a predetermined pressure, aspreviously described, to limit the amount of pressure generated by thesyringe.

Another embodiment of the syringe assembly of the present invention isillustrated in FIGS. 17 and 18, in which like reference numeralsdesignate like parts. In this embodiment, a balloon 40' has itsperipheral edges 44'sealed by suitable means 46', such as adhesive, tothe outer surface 152 of the syringe 22 to define the cavity 48, whichcommunicates with the chamber 26 through the opening 42. The balloon40'inflates at a predetermined pressure, as previously described tolimit the amount of pressure generated by the syringe.

Another embodiment of the syringe assembly 20 of the present inventionis illustrated in FIG. 19, in which like reference numerals designatelike parts. In this embodiment, the extensions 34 described inconnection with FIGS. 4-14 may be permanently affixed to the syringe tip36' by suitable means 150, such as adhesive. As shown in FIG. 20, theextensions 34 may be constructed as an integral part of the syringe 22,if desired.

Another embodiment of the syringe assembly of the present invention isillustrated in FIG. 12, in which like reference numerals designate likearts. In this embodiment, the barrel 24 of the syringe 22 istransparent, and the plunger 28 has a flexible plug 30 adjacent the oneplunger end 32 which is received in the syringe chamber 26. The one end32 of the plunger 28 includes a centrally located transparent member 90having a cavity 92 facing the syringe chamber 26, with the transparentmember 90 being visible through the barrel 24. A flexible diaphragm 94is supported by the plug 30 and extends across an opening 96intermediate the cavity 92 in the transparent member 90 and the syringechamber 26. When a predetermined pressure has been attained in thesyringe chamber 26, the diaphragm 94 flexes from a first positionadjacent the opening 96, as shown by solid lines in the drawing, to asecond position received in the transparent member 90, as shown bydotted lines in the drawing. The diaphragm 94 is thus visible to theuser in its second position and serves as an indication that thepredetermined amount of pressure has been reached in the syringechamber, and that the user should cease pumping the syringe.

A further embodiment of the syringe assembly of the present invention isillustrated in FIG. 13, in which like reference numerals designate likeparts. In this embodiment, the plunger 28 has a flexible plug 30'adjacent the one plunger end 32 which seals against the inner surface 33of the barrel 24. The plug 30' has an annular slot 100 having one end102 communicating with the syringe cavity 26, and defining an annularflexible side wall 104 of the plug 30' adjacent the inner surface 33 ofthe syringe barrel 24. The side wall 104 of the plug 30' flexesresponsive to a predetermined pressure in the syringe chamber 26, andengages against the inner surface 33 of the syringe barrel 24 to impedemovement of the plunger into the syringe chamber. Thus, when thepredetermined amount of pressure is generated by the syringe, resistanceto movement of the syringe plunger 28 into the syringe barrel 24 becomesnoticeable to the user, the movement of the plunger is then stopped toprevent damage to the patient.

Thus, there has been described a syringe assembly which has means forlimiting the amount of pressure generated by the syringe assembly toprevent harm to a patient. In addition, the syringe assembly indicatesto the user when the predetermined amount of pressure has been reached.

According to the present invention, methods are also provided forperforming an epidural and a spinal anesthesia procedure. In a spinalanesthesia procedure, the tip of a needle, used to perform theprocedure, is advanced through the body tissue t, the epidural space e,which is at a slight negative pressure, and the dura mater d into thesub dural space s, which is at a positive pressure, as previouslydescribed in connection with FIG. 1. According to a method of thepresent invention, a balloon of the adapter in the syringe assembly isselected to inflate at a first predetermined pressure less than thepressure in the sub dural space, and a balloon on the syringe, which isremovably attached to the adapter, is selected to inflate at a secondpredetermined pressure greater than the pressure in the sub dural space.When the needle tip T pierces the dura mater d and enters the sub duralspace s, fluid in the space actuates the balloon on the adapter due tothe higher pressure in the space relative the first predeterminedpressure, thus indicating that the needle tip is at the proper locationin the space for performing the spinal anesthesia procedure. The adaptermay be removed from the needle and syringe, and the syringe is attachedto the needle to eject anesthetic solution into the sub dural space. Theballoon on the syringe limits the amount of pressure generated by thesyringe to prevent harm to the patient, as previously described.

Alternatively, first and second adapters may be used in conjunction witha standard syringe, the first adapter having a balloon inflatable at thefirst predetermined pressure, and the second adapter having a ballooninflatable at the second predetermined pressure. The balloon of thefirst adapter is utilized to determine when the needle tip is located inthe sub dural space, after which the first adapter is replaced with thesecond adapter for pumping the anesthetic solution into the space.

A method is also provided for performing an epidural anesthesiaprocedure with the syringe assembly of the present invention. After thetip of a needle, attached to a syringe or an adapter and syringe, isadvanced nto the body tissue, the syringe plunger is pushed sufficientlyinto the syringe chamber to inflate a balloon on the syringe assemblywith anesthetic solution from the chamber. The needle tip is thenadvanced toward the epidural space. When the needle tip enters theepidural space the solution from the syringe assembly flows into thespace due to the pressure generated by the inflated balloon relative thenegative pressure in the space. Thus, the balloon deflates and indicatesto the user that the needle tip is properly located for performing theprocedure. The anesthetic solution may then be ejected from the syringeinto the epidural space. Accordingly, the method of the inventionprevents the user from improperly puncturing the dura mater during theepidural anesthesia procedure.

The foregoing detailed description is given for clearness ofunderstanding only, and no unnecessary limitations should be understoodtherefrom, as modifications will be obvious to those skilled in the art.

We claim:
 1. A syringe, comprising:a transparent barrel having a chamberfor retaining fluid; an elongated plunger having one end received in andclosing the chamber for pumping fluid out of the chamber, said oneplunger end including a hollow transparent member having a cavity facingthe chamber through an opening and being visible outside the barrel,means for sealingly engaging against an inner surface of the barrel, andan elastic diaphragm being permanently secured to the plunger andextending across said opening and closing the cavity, said diaphragmflexing into the transparent member responsive to a predeterminedpressure in the chamber to indicate when the pressure in the chamber isabove the predetermined amount.